Data Over Cable Service Interface Specification (DOCSIS) is an international telecommunications standard that details various aspects of providing and handling high-speed data transfer using cable TV (CATV) systems that employ coaxial cabling as a medium of transmission. DOCSIS is followed by many cable television operators to provide Internet access over existing proprietary cable system infrastructure. Further, the DOCSIS standard allows for many variations within systems for accomplishing data communications so long as the standard is met. As a result, many devices may employ vastly different mechanisms and algorithms for accomplishing data communication all within the standards of DOCSIS.
Modulated signals containing data being communicated over a cable are received by a DOCSIS device, such as a cable modem (CM), and are thereafter demodulated to provide corresponding Ethernet packets. The cable modem includes an Internet Protocol (IP) filter that is used to filter and route these Ethernet packets to the appropriate components within the cable modem and to devices coupled to the cable modem. Conventionally this filtering is done by a processor contained in the cable modem, where the processor executes software to parse incoming Ethernet packets and thereby obtain the IP and other protocol information contained therein. The processor thereafter applies the desired filtering to the packet based on this information and on filter information stored in the cable modem, and either forwards or drops the packet as appropriate. This filtering needs to be done extremely quickly so that the Ethernet packets are not excessively delayed by the cable modem, but performing this function is extremely computationally intensive for the processor. Improved methods and devices for performing the required IP filtering are accordingly needed.